The present invention relates generally to the making, filling and closing of containers of thermoplastic material, and more particularly to a novel method of making, filling and closing containers of thermoplastic material and to an apparatus for carrying out the method.
It is already known to make containers from thermoplastic material by extruding the material from an extrusion head, expanding the extruded tubular thermoplastic material by blow-molding to the shape of a container, and thereafter fill the container by means of a filling tube which is located within the extrusion head nozzle. Subsequently, transversely movable welding elements close the upper end of the filled container and the container is then placed onto a conveyor for removal.
It is also known to extrude a tube of thermoplastic material and to surround it by partible molds which move at the same speed at which the continuously extruded thermoplastic tube moves. The increment of the tube that is enclosed in the mold is then expanded by blow-molding to form a container which is filled while it is still connected with the advancing extruded tube, and which is thereupon closed by welding and separated from the tube. The extruded thermoplastic tube is initally deformed in the neck and bottom regions of the container by individual neck and bottom forming devices, and only subsequently is it deformed intermediate these regions to form the major part of the container. In between these operations a previously formed container is filled while the tube increment located in the upper or preceding mold is being expanded, and the container that is being expanded is supported only at its bottom. This prior-art approach requires a great number of individual components for an apparatus to carry it into effect, since the bottom and neck regions of the container are formed separately from one another, and then the major portion of the container is also formed separately, and all of these components must be operated in timed relationship which requires substantial maintenance and therefore labor expenses. Also, it is very difficult to appropriately center the mold sections due to wear and other problems, and it is impossible to produce sterile containers in this manner since the blow-molding and filling tube which follows the movement of the molds is made to travel freely and unprotectedly through the atmosphere during the idling phase, where it can become contaminated.
Still other prior-art approached are known and also suffer from various disadvantages which make them unsuitable for many applications.